Resonant Prepare for BLACK AUTUMN, c. 1960s Large Pinback Button

I have done a fair bit of searching but have not placed the precise origins of this pinback button, though I am quite confident 1960s and presume Civil Rights connected. (With the font used for "Black Autumn" very close to the that used for the now iconic " I Am a Man" posters of the 1968 Memphis sanitation strike.) Found now, out of time and place, it seems to me to resonate all the more broadly, invoking everything from the November elections and their potential implications to (hopefully not for) the apocalypse itself.

2 1/2" d and in good vintage condition, with the black a bit silvery and a few small spots of rust on the button back.